Manufacture of fluorinated organic compounds



United States Patent MANUFACTURE OF FLUORINATED ORGANIC COMPOUNDS NoDrawing. Application January 22,1957

Serial No. 635,128

12 Claims. (Cl. 260-653) This invention relates to a method for makingfluorinated organic compounds and in particular to a process, forcoupling certain perfluoroand perfluorochloroalkyl iodides.

Highly fluorinated organic compounds have come into increasing use inrecent years as lubricants, dielectrics, fire-extinguishers, heattransfer media, solvents, plasticizers, gasket and valve packings andprotective coatings. They are especially desirable because of theirgreat stability at high temperatures and chemical inertness.

One method of making relatively long chain fluorinated compounds is bythe so-called telomerization technique in which a fiuorinated iodide,AI, is reacted with an unsaturated fluorinated compound, B, to givecompounds having the general formula A(B),,I where n is from 1 to say20. "The presence of the iodine atom at the end of the chain in suchcompounds decreases their stability and before they can be put topractical use it is usually necessary to stabilize them. One way inwhich such compounds may be stabilized is to couple two. moleculestogether, eliminating iodine. and forming a. chain having twice thelength of the original. Previous techniques for carrying out suchcoupling reactions have in many cases involved the use of metallicmercury and ultraviolet radiation which is expensive andnot well suitedto industrial techniques.

It is an object of thepresent invention to providea method for couplingcertain. highly fluorinated iodides which is simple and economical tocarry out.

It is another object of the invention to provide a method for couplingfiuorinated iodides in which the use of metallic mercury is eliminated.

It is another object of the invention to provide a method forthecoupling of certain fiuorinatediodides in which heat is used tosupply energy for the reaction.

In accordance with the invention these objectives are attained by meansof a process which comprises heating perfluoroor perfluorochloroalkyliodides having the structure in the presence of mercuric oxide. In theabove formula R is selected from the group consisting of chlorine,fluorine, and alkyl, fluoroalkyl, chloroalkyl and fluorochloroalkylradicals having not more than about 6 carbon atoms. Preferably R is aperfluoro alkyl radical, e. g. --C,,,F where m is not greater than 6 ora perfiuorochloroalkyl radical having not more than about 6 carbonatoms. As used herein the term perfluorochloro means a radicalconsisting of carbon, fluorine and chlorine having more fluorine thanchlorine. lln the formula X is selected from the group consisting ofchlorine and CF radicals, and n is an integer from 1 to about 20,preferably from 1 to say 10. The invention is particularly applicable toperfluoroalkyl and perfluorochloroalkyl iodides such, for example, ascompounds of the type C F-;[CF CF(CF )],,I and is required to obtain asatisfactory yield.

2,884,466 PatentedApr. 28, 1959 2 whose preparation is described in ourcopending application Serial No. 614,821, filed October 9, 1956; and toperfluorochloroalkyl iodides of the type CILCF CFCIl I, whosepreparation is described in R. N. Haszeldine, Journal of the ChemicalSociety (London), December 1955, pages 4291 to 4302 inclusive. Thecompounds obtained by the coupling reaction will in general have theformula where R and X are as indicated above.

It will. be understood that a mixture of two. or more different iodidesconforming to the general formulas given above may be mixed and reactedsimultaneously to give mixed products.

The conditions of reaction are subject to considerable variation. Thetemperature at which the reaction is con ducted may range from about 150to about 350 C., preferably from about 170 C. to about 250 C.

Pressure is not a critical factor. The reaction is generally carried outbetween about 1 mm. Hg and about 1000 atm. usually between about 1 atm.and about 100 atm.

The proportion of mercuric oxide which is used may range from about 0.1to about 10 mols per mol of iodide, preferably between about 1 and about5 mols. The mercuric oxide is usually introduced as a powder; however itmay be used in other physical forms, for example as pellets or granules.

The reaction time is not critical and will be whatever It may range fromabout 1 minute to about 100 hours, and is normally between about hourand about 20 hours.

The technique used in effecting the reaction is also not critical. Thereaction may be carried out by introduc- I ing the iodide, or iodides,and mercuric oxide into a sealed vessel made of some inertmaterial suchas Pyrex or Monel and heating for whatever time is required, to completethe reaction. Alternatively the reaction mixture may be circulatedthrough a heated tube. Other conventional techniques may also be:employed.

The invention will be further described in the following examples. It isunderstood that the examples are given for purposes of illustration onlyand are not to be taken as in any way restricting the invention beyonthe scope of the appended claims. Example 1.-A mixture of2-iodoperfluoro'hexane (5 g., 0.011 mol) and powdered yellow mercuricoxide (3 g., 0.014 mol) was. sealed in a heavy-walled Pyrex tube andheatedfirst at 148 C. for 40 hours and then at 235 C. for 15 hours. (Oninitial mixing the pink iodine color was bleached and on gentle heatingan exothermic reaction was observed.) The tube was then cooled andopened. The 1.5 g. of product which'could be transferred .in vacuo (withwarming of the tube) .was shown to be perfluoro-S,G-dimethyldecane,boiling point C. at 45 mm., n =l.2945.

Example 2.-The procedure of Example 1 is followed using C F [CF CF(CF Ias the iodide. The coupled product C3F7 13 3C3F7, circa C., n =1.3137,is obtained.

Example 3.Two reactions using CF C1CFCII were carried out in sealedCarius tubes. The first reaction was carried out at 232 C. for two daysusing 5.6 g. of CF ClCFClI and 6.51 g. of yellow mercuric oxide. Thesecond reaction was conducted at 220 C. for 18 hours using 28 g. of CFClCFClI and 43.2 g. of yellow mercuric oxide. The coupling compound wasclearly shown by infrared spectroscopic analysis to be among theproducts formed in both cases. The conr I r 2,884,466

version to cr,c1crc1cr=c1cr=,c1 was approximately in both reactions.

Example 4.The procedure of Example 3 is followed using Cl(CF CFCl) I asthe iodide. The coupled product Cl(CF CFCl) (CFClCF Cl, 3.1. 195-200 C.at about 0.1 mm. Hg, is obtained.

Example 5 .The compound CF CICF(CF [CF CF(CF 1 1 is heated at about 235C. with a 100% molar excess of HgO. The coupled product CF,ClCF(CF [CFCF (CF l (CF CFCFfl 2 (CF, CFCFQCI is obtained. 1

From a consideration of the foregoing description it will be seen thatthe present invention provides a simple and efiicient way of couplingfluoro iodides of the type referred to. By eliminating metallic mercuryand ultraviolet radiation used in prior processes, the need for spe-'cial apparatus and safety provisions is lessened. The invention thusprovides a technique well suited to industrial applications. I

The products which may be made by means of the novel process are usefulas lubricants, heat. transfer media, solvents, plasticizers and in ahost of other appli-- cations. For example, the compoundperfiuoro-5,6-dimethyldecane whose preparation is described in Example 1is a-good dielectric andis useful as a condenser fluid.

The products obtained in Examples 2 and 5 have been used as plasticizersfor polytetrafluoroethylene plastic and as thermally and chemicallystable lubricants. In one instance a polytetrafiuoroethylene tape, 5mils thick and 0.1 inch wide, was immersed in the product of ExampleWhat is claimed is:

1. A method for coupling fluoroalkyl iodides having the formula:

RECF CFXI ,,I

where R is selected from the group consisting of chlo-' rine, fluorineand alkyl, fluoroalkyl, chloroalkyl and fluorochloroalkyl radicalshaving not more than about 6 portion of mercuric oxide used is betweenabout 0.1 and about 10 mols, per mol of iodide.

4. The method claimed in claim 1 wherein the iodide has the formula C 13[CF CF(CF ],,I

5. The method claimed in claim 1 wherein the iodide has the formula I 6.The method claimed in claim 1 wherein the iodide has the formula CFC1CF(CF [CF CF(CF ],,I

7. A method of coupling the compound 2-iodoperfiuorohexane whichcomprises heating said compound in the presence of mercuric oxide. Y

8. A method of coupling the compound CF CICFCII which comprises heatingsaid compound in the presence of mercuric oxide.

9. A method of making compounds having the structure where R is selectedfrom the group consisting of chicrine, fluorine, and alkyl, fluoroalkyl,chloroalkyl and fluorochloroalkyl radicals having not more than about 6carbon atoms, where X is selected from the group consisting of chlorineand the CF radical, and where n is an integer from. 1 to about 20 whichcomprises heating fluoroalkyl iodides having the formula homologuecoupling products have been used as lubricarbon atoms, where X isselected from the group consisting of chlorine and the -CF radical,and.where n is 'an integer from 1 to about 20, which comprises heatingsaid iodides in the presence of mercuric oxide.

2. The method claimed in claim 1 wherein the iodides are heated atbetween about C. and about 350 C.

3. The method claimed in claim 2 wherein the pro RliCF -CFX] ,1

where R and X are as defined above, in the presence of mercuric oxide.

10. A method of making perfluoro-S,G-dimethyldecane which comprisesheating 2-iodoperfluorohexane in the presence of mercuric oxide.

11. A method of making the compound CF CICFCICFCICECI which comprisesheating the compound CF ClCFClI in the presence of mercuricoxide.

12. A method of making the compound which comprises heating the compoundCFQCICF (CF [CF CF (CF 1 1 in the presence of mercuric oxide.

References Cited in the file of this patent UNITED STATES PATENTSFeasley Sept. 30,

OTHER REFERENCES Henne et 21].: Tour. Amer. Chem. Soc.," vol. 73, April1951, p. 1791.

1. A METHOD FOR COUPLING FLUOROALKYL IODIDES HAVING THE FORMULA: